Although high-dose chemoradiotherapy with autologous stem cell transplantation has shown some promise in the management of pts. with multiple myeloma, relapse of the underlying disease remains the primary cause of treatment failure. This is a pilot study to explore the possibility that active-specific immunotherapy may be effective in eliminating minimal residual disease remaining after high-dose therapy. Experimental studies in pts. with lymphoma, as well as a single pt. with myeloma have demonstrated the feasibility of immunoglobulin idiotype as a tumor-specific antigen for development of therapeutic vaccines against B-cell malignancies. Pts. will be immunized with myeloma idiotype protein, made immunogenic by conjugation to a carrier (KLH) and administration with GM-CSF as an immunological adjuvant, at several timepoints before and after high-dose therapy. The objective of this study is to test whether cellular and humoral immunity can be induced against the unique idiotype expressed on the patient's myeloma pre- and post-transplantation. Pts. will receive a series of 3 vaccinations with myeloma Id-KLH (0.5 mg) administered s.c. together with GM-CSF (250 microgram/mg2) for 4 consecutive days within 8 weeks of high-dose therapy with either melphalan/TBI or melphalan/cytoxan followed by autologous peripheral mononuclear stem cell transplantation. Pts. will then be revaccinated with the same vaccine formulation 2, 3, and 6 months post-transplantation. We plan to accrue 20 pts. to this study. An initial analysis of results will be performed after 3 pts. receive an autologous transplant. If none of these 3 pts. shows an idiotype-specific humoral and/or cellular response post-transplantation, this study will be terminated.